Different designs of automated transmissions (ASG) have long been constructed as an automated transmission with a single disconnection type clutch as well as constructed as an automated dual-clutch transmission (DKG) with two decoupler type clutches respectively allocated to one of two gear trains, which are also used in production vehicles. The control device of an automated transmission comprises gear actuators, like gear regulators for engaging and disengaging gears and a clutch actuator for engaging and disengaging a decoupler type clutch disposed in the flow of power between the internal combustion engine and the transmission input shaft, as well as control elements for controlling the gear actuators. Similarly, the control device of an automated dual-clutch transmission comprises gear actuators for each of both gear trains, like gear regulators for engaging and disengaging the allocated gears and a clutch actuator for engaging and disengaging a disconnection type clutch disposed in the flow of power between the internal combustion engine and the transmission input shaft, as well as control elements for controlling the gear actuators.
As a result of the energy density, good control properties and availability of technically advanced components, the control devices of automated transmissions and automated dual-clutch transmissions are mostly constructed hydraulically, which means that the corresponding speed selectors and clutch actuators are constructed as hydraulic control cylinders and the allocated control elements as hydraulic selector or control valves.
The selector and control valves can be executed as solenoid valves, and can be directly controlled via an electric control current in this design. As this, however, requires correspondingly strong solenoid valves of relatively large dimensions and comparatively large weights as well as relatively high electrical control currents, the selector and control valves are preferably constructed as pressure-actuated, and in this design mostly controllable as pilot valves constructed as smaller solenoid valves.
In particular, in the case of heavy commercial vehicles, which are equipped with a pneumatic pressure supply device for the power supply, a pneumatic configuration of control devices of corresponding step-by-step variable speed transmissions with a largely identical layout and mode of operation is alternatively possible. Therefore, the present invention likewise comprises pneumatic control devices, even if herein after only hydraulic control devices will be mentioned for the sake of achieving uniform wording.
A hydraulically activatable decoupler type clutch of an automated step-by-step variable speed transmission (ASG, DKG) can be executed as a wet multi-disk clutch or as a single-disk or multi-disk dry clutch. The decoupler type clutch is usually constructed actively engagable so that it can be engaged by feeding hydraulic pressure medium via the allocated clutch control valve into the pressure chamber of the clutch control cylinder and be disengaged via the discharge of the pressure medium from the pressure chamber and/or by the depressurization of the pressure chamber of the clutch control cylinder via the clutch control valve. In consequence, the decoupler type clutch will open in case of a disturbance in the allocated control device due to an interruption of the allocated control signal, in particular, of the control pressure of the allocated pilot valve because of the associated unpressurized shifting of the pressure chamber of the control clutch cylinder.
In a vehicle equipped with an automatic transmission with only one decoupler type clutch, in the event of a disturbance while the vehicle is standing still the vehicle is prevented from starting, and in the event of disturbance while the vehicle is moving, the vehicle is forced to coast. Although this control behavior of the control clutch is advantageous in most driving situations, in certain cases, like for example a vehicle stop in a danger area, when driving on an expressway with dense traffic and at high speed, or when driving along an extended incline, this can lead to undesirable situations.
A corresponding hydraulic control device of a dual-clutch transmission is, for example, known from DE 101 34 115 A1. For each of the two gear trains, this control device has an independent control circuit with gear regulating valves for controlling two pressure chambers of several gear regulators, with a multiplex valve for connecting both gear regulating valves to each of the gear regulators, and a clutch control vale for controlling the allocated decoupler type clutch. Both control circuits can respectively be connected to and/or depressurized and separated from the main pressure line via an own safety valve, respectively constructed in that description as a 3/2-way solenoid switching valve. In case of a one-gear disturbance involving only one control circuit, the corresponding control circuit can be depressurized by disconnecting the allocated safety valve, as a result of which the allocated gear train is put out of operation by disengaging the corresponding decoupler type clutch. Driving can than be continued in emergency operation via the other gear train, however, taking into account large gear transitions, whereby each shifting process is associated with traction force interruptions, so that leaving the danger area and reaching a repair shop can at least be possible. If, however, a main disturbance involving both gear trains and/or a superordinate electronic transmission control (EGS) occurs, both safety valves are disconnected and thus both gear trains put out of operation by disengaging the decoupler type clutches. This necessarily results in a vehicle breakdown which can only be acted upon to a limited extent by the driver with the already mentioned disadvantages.
In order to avoid this unfavorable control behavior in the event of a disturbance, a hydraulic control device of an automated step-by-step variable speed transmission (ASG+DKG) is provided in DE 10 2604 020 569 A1 having a self-retaining valve disposed in the pressure supply branch of the clutch control valve for the rotational speed-dependent emergency actuation of the decoupler type clutch. Apart from a control pressure that is available during normal operation, the self-retaining valve is also acted upon by a permanently available rotational speed-dependent control pressure, which in an offset operating position conveys an activation control pressure to an activation valve. The activation valve is likewise kept in an offset operation position by a control pressure that is available during normal operation, whereby the activation pressure conveyed is shut off in this position. In case of a disturbance, the control pressures that are available during normal operation drop or at least strongly decrease. As a result of this, the activation valve is placed in idle position by means of a valve spring, where the activation pressure is conveyed further into a front side pressure chamber of the clutch control valve facing away from the spring. Thus, the clutch control valve is kept in an operating position or is moved into it, where the pressure chamber of the clutch control cylinder is acted upon with an operating pressure, and the decoupler type clutch is thus kept engaged and/or is disengaged, as a result of which further driving of the vehicle in the emergency operation is possible.
This retaining function of the decoupler type clutch is, however, only available with a sufficiently high rotational speed-dependent control pressure, which can be proportional to the speed of the drive motor, or proportional to the speed of the transmission output shaft and so to the vehicle speed. If the rotational speed-dependent control pressure is below a predetermined threshold value, by means of its valve spring the self-retaining valve will go to the idle position, in which the activation pressure is locked. Without the application of the activation pressure, the clutch control valve, however, also goes to its idle position, in which the pressure chamber of the valve control cylinder is depressurized and the disconnection type clutch is thus be opened. In consequence, it is advantageously ensured that a motor stall associated with the disturbance of safety-relevant servo drives, like possibly of a negative pressure-driven brake force booster or a mechanically driven servo pump of a servo steering mechanism, is avoided, and that coasting, which the driver can only act upon to a limited extent, is made possible.
In addition, in the corresponding control device of a dual-clutch transmission, a clutch selector valve downstream of the activation valve and acted upon in the opposite direction of the operating pressures facilitates conveying the activation pressure put through by the activation valve only to the clutch control valve of the clutch control cylinder acted upon with the higher operating pressure at the moment of the disturbance. The outcome is that the decoupler type clutch, which is still engaged at the moment of the disturbance, is completely engaged and subsequently kept engaged, and the other decoupler type clutch is completely disengaged as long as the speed of the drive motor and/or of the output shaft of the dual-clutch transmission is sufficiently high.
Despite the advantageous functional advantages of the above described control device, an improvement regarding the possibility of engaging a gear in the engaged idle position N exists. Thus, in certain driving situations of vehicles equipped with automated step-by-step variable speed transmissions acceleration of the impending shifting processes is desirable, as with multiple changes between the reverse position R via the idle position N to the forward position D, or when changing from the idle position N to the forward position D, engaging one gear in the already engaged idle position N in an automated transmission, and possibly engaging two gears in an automated dual-clutch transmission (DKG).
If, for example, shifting to and fro between the reverse position R and the forward position D is recorded by corresponding sensors when the vehicle is standing still or moving at very low speed, as a result of which a free rocking motion of the vehicle, e.g. in the snow or marshes, is detected, the corresponding shifting processes can be significantly accelerated by engaging both gears (R, G1) in an automatic transmission by engaging the reverse gear R or first gear G1, and in an automatic dual-clutch transmission by the usual allocation of the reverse gear R and first gear G1 to different gear trains, as, once the respective position (R or D) for accomplishing the forward thrust of the vehicle by the selector lever is reached, only the decoupler type clutch has to be engaged in an automated transmission, and only one of both decoupler type clutches has to be engaged in the automatic dual-clutch transmission.
Likewise, when an impending sportive racy start-up of an automatic dual-clutch transmission is requested by the driver, the starting process can be considerably accelerated with the usual allocation of the first gear G1 and the second gear G2 to different gear trains by already engaging both gears (G1, G2) with the still engaged idle position N, as only the decoupler type clutch of the start-up gear G1 has to be engaged in the first instance when the gear position D is engaged, and subsequently the power flux can rapidly be diverted to the second gear G2 by an overlapping actuation of both decoupler type clutches.
A further driving situation, in which the engagement of a gear with disengaged idle position N is advantageous, is so called gliding and/or coasting, in which the driver accelerates the vehicle to a certain speed, and the vehicle subsequently coasts with engaged idle position N or at least disengaged drive clutch. In this coasting phase, the driver can, however, return to the forward position D and/or engage the drive clutch at any time, and demand a more or less high propulsive performance. If a gear corresponding to the current speed is already engaged, the decoupler type clutch only has to be engaged in an automated transmission, and the only decoupler type clutch of the involved gear train has to be engaged in an automatic dual-clutch transmission, as a result of which a very rapid vehicle response is ensured. However, to be able to engage a gear in disengaged idle position N, it must at any rate be ensured that in case of a disturbance in the electronic transmission control (EGS) or in an element of the hydraulic control device, the decoupler type clutch involved is not inadvertently engaged.
Against this background, it is the object of the present invention to propose a hydraulic control device of an automated step-by-step variable speed transmission of the above mentioned type, which is improved with regard to enabling a safe idle gear engagement, constructed as simple and cost-effective as possible and without functional restrictions.
Therefore, according to the characteristics of the main claim, the present invention proceeds from a pressure medium-actuated, i.e. hydraulically or pneumatically actuated control device of an automated step-by-step variable speed transmission (automated transmission or automatic dual-clutch transmission), with a selectable clutch control valve for controlling a clutch control cylinder of an actively engageable decoupler type clutch disposed in the power flux between the drive motor and the input shaft of the step-by-step variable speed transmission, and having a self-retaining valve disposed in the pressure supply branch of the clutch control valve for the rotational speed-dependent emergency actuation of the decoupler type clutch. In order to attain this object, an electrically selectable disconnection actuator is provided, which is constructed and operatively connected to the self-retaining valve such that the valve piston of the self-retaining valve can be moved into an idle position locking the pressure supply of the clutch control valve in the powered state of the switch-off actuator, and into an operating position determined by the applied control pressures in the powered-off state of the disconnection actuator.
By supplying the relatively simply and cost-effectively configurable disconnection actuator with current, the hydraulic control device of the valve piston of the self-retaining valve is displaced to its idle position during normal operation, and thus a supply pressure P_1 conveyable to the clutch control valve or a control pressure conveyable by the self-retaining valve, by means of which the conveyance of the supply pressure P_V1 can be controlled via another control valve, is locked, and the corresponding connection line depressurized. By omitting the supply pressure P_V1 in the corresponding clutch control cylinder, the allocated decoupler type clutch is necessarily disengaged or, if it is already in the disengaged state, is held securely disengaged. In this operating situation, with the idle position N engaged, in particular for acceleration of impending shifting processes, one gear can be engaged in an automatic transmission, and up to two gears can be engaged in an automatic dual-clutch transmission without the possibility that, in case of a disturbance in the hydraulic control device, or in the allocated electronic transmission control (EGS), a decoupler type clutch can unintentionally be engaged.
To terminate this operating situation the switch-off actuator is again switched off, whereby the valve piston of the self-retaining valve again returns to the operating position taken before switching on the disconnection actuator under the impact of available control pressures, in particular of a control pressure P_Nor that is available during normal operation, and thus the self-retaining valve goes to the previous operating state previously overdriven by the disconnection actuator.
If, however, the hydraulic control device is already operating in emergency operation, where all electrically controllable control elements of the hydraulic control device are in the power-off state, the disconnection actuator can no longer be activated. From this, there results in that in emergency operation, the corresponding functionalities, like engaging a gear in an engaged idle position N, are no longer available.
The switch-off actuator can be constructed as a hydraulic solenoid switching valve, e.g. as a 3/2-way switching valve, with a connection of a switching pressure supply line conveying a reduction pressure P_Red, with a connection of a control pressure line connected to a front side pressure chamber of the self-retaining valve containing the valve spring, and with a connection of a depressurized line, by means of which the switching pressure is connected to the depressurized line in the power-off state and to the control pressure supply line in the powered state. It goes without saying that in this case the switch-off pressure P_Abs through-switchable via the solenoid switching valve, which largely corresponds to the reduction pressure P_Red, is higher than the maximum required switching pressure of the self-retaining valve and/or that the through-switchable switch-off pressure P_Abs of the solenoid switching valve as well as that the spring constant of the valve spring and the pressurized active surfaces of the valve piston of the self-retaining valve are dimensioned such that the pressure and spring forces acting together with the switch-off pressure P_Abs upon the valve piston in the engagement direction in each case are higher than the maximum pressure forces acting upon the valve piston in the opening direction.
As an alternative, the disconnection actuator can, however, also be constructed as a hydraulic solenoid control valve, e.g. as a 3/2-way control valve or as a 3/3-way control valve, with a connection of a control pressure supply line conveying a reduction pressure P_Red, with a connection of a control pressure line connected to a front side pressure chamber of the self-retaining valve containing the valve spring, and with a connection of a depressurized line, by means of which the switching pressure line is connected in the power-off state, and to the control pressure supply line in the powered state. In this connection, it is provided that the maximum switch-off pressure P_Abs_max adjustable via the solenoid control valve, which largely corresponds to the reduction pressure P_Red, is higher than the maximum required switching pressure of the self-retaining valve and/or that the maximum adjustable switch-off pressure P_Abs_max of the solenoid control valve as well as the spring constant of the valve spring and the pressurized active surfaces of the valve piston of the self-retaining valve are dimensioned such that the pressure and spring forces acting together with the switch-off pressure P_Abs upon the valve piston in the engagement direction in each case are higher than the maximum pressure forces acting upon the valve piston in the disengagement direction.
In the construction of the switch-off actuator as a solenoid control valve, at least one further switching pressure line leading to another hydraulically controllable switching control element can be connected to the switching pressure line or directly to the connection of the switching pressure line of the solenoid control valve, whereby the switching pressures of the self-retaining valve and of the other switching control element are conveniently of different height.
In this way, three control states for the disconnection actuator and/or the solenoid control valve result; a first control state, in which both switching control elements are not commutated, a second control state, in which only one of both switching control elements is commutated, and a third control state, in which both switching control elements are commutated.
In order to achieve a relatively simple and effective layout, in a preferred embodiment the self-retaining valve is provided with a concentric pressure chamber, which on the spring side has a controllable connection of a supply line conveying a supply pressure P_V1, which concentrically has a connection of a connection line leading to the supply connection of the clutch control valve, and which has a controllable connection of a depressurized line on the side facing away from the spring, and which concentrically has a further a control pressure line that during normal operation conveys a control pressure P_N, and which is restricted by a larger active surface of an adjacent piston collar on the spring than on the side facing away from the spring, and with a front-side pressure chamber containing the valve spring, which has a connection of the switching pressure line leading to the disconnection actuator, as well as with a front-side pressure chamber facing away from the valve spring, which has a closable connection of a control pressure line conveying a rotational speed-dependent control pressure P_D.
By means of the hereby provided direct conveyance of the supply pressure P_V1 through the self-retaining valve, an activation valve provided in the control device according to DE 10 2004 020 569 A1 can advantageously be spared. The above described resetting function of the valve piston via the control pressure P_Nor after switching off the disconnection actuator is performed in this case by the different size of the active surfaces of the adjacent piston collars that limit the corresponding pressure chamber. Here, the respective connection is controlled, i.e. opened and closed, in the manner known per se via a control edge of an adjacent piston collar of the valve piston on the spring side or on the side facing away from the spring.
In order to increase the functional reliability of the disconnection function of the disconnection actuator the self-retaining valve can additionally be provided with a further concentric pressure chamber, via which a control pressure supply line conveying the reduction pressure P_Red can be connected to a control pressure supply line leading to a front side pressure chamber of the clutch control valve facing away from the valve spring and provided with a locking element, the pressure chamber having a controllable connection of the control pressure supply line on the spring side, concentrically a connection of the control pressure supply line, and a controllable connection of a depressurized line on the side facing away from the spring.
While allowing for a correspondingly higher constructive expenditure for the self-retaining valve in the powered state of the disconnection actuator, besides the supply pressure P_V1, the reduction pressure P_Red, which in the operating mode is conveyed as emergency pressure to the front-side pressure chamber of the clutch control valve via the locking element, is likewise shut off.
As an alternative to the above described both embodiments of a single self-retaining valve, two pressure controlled self-retaining valves can also be provided, of which the first self-retaining valve is provided with a concentric pressure chamber, which on the spring side has a controllable connection of a supply line conveying the supply pressure P_V1, which concentrically has a connection of a supply pressure connection line leading the supply connection of the clutch control valve, and which on the side facing away from the spring has a controllable connection of a depressurized line, whereby the pressure chamber is restricted on the spring side by the active surface of an adjacent piston collar that is larger than on the side facing away from the spring, as well as with a front side pressure chamber containing the valve spring, which has a connection of the switching pressure line leading to the switch-off actuator, and with a front-side pressure chamber facing away from the valve spring, which has a controllable connection of a control pressure line conveying a control pressure P_Nor during normal operation, which is restricted by the control edge of an adjacent piston collar on the spring side.
The second self-retaining valve is provided with a concentric pressure chamber, via which a control pressure supply line conveying the reduction pressure P_Red can be connected to a control pressure connection line leading to a front side pressure chamber of the clutch control valve facing away from the valve spring and provided with a locking element, whereby this pressure chamber has a controllable control pressure supply line on the spring side, concentrically a connection of the control pressure supply line, and a controllable connection of a depressurized line on the side facing away from the spring, as well as with a font side pressure chamber facing away from the valve spring, which has a controllable connection of a control pressure line conveying a rotational speed-dependent control pressure P_D.
In this variant, both self-retaining valves are executed in a relatively simple and space saving manner. The first self-retaining valve is used for conveying and shutting off the supply pressure P_V1, whereby the corresponding valve piston is displaced via the control pressure P_Nor available during normal operation to an operating position with open conveyance of the supply pressure P_V1, and in case of a disturbance, i.e. when the control pressure P_Nor is not available, kept in the current operating position by the supply pressure P_V1 via the active surfaces of different sizes of the adjacent piston collars.
If necessary, however, the valve piston can be displaced to the idle position with shut off conveyance of the supply pressure P_V1 by supplying the disconnection actuator with current by means of the switch-off pressure P_Abs then active in the switching pressure line largely corresponding to the reduction pressure P_Red.
The second self-retaining valve is used for conveying the reduction pressure P_Red to the locking element and from there in emergency operation as emergency control pressure P_Not on to the front side pressure chamber of the dutch control valve. In case of a disturbance, i.e. when the control pressure P_Nor is not available, the corresponding connection is only kept open by the front side application of the rotational speed-dependent pressure P_D to the valve piston when the speed of the drive motor or of the output shaft of the step-by-step variable speed transmission is sufficiently high, and shut off when the speed is too low. Thus, both self-retaining valves together approximately fulfill the same scope of functions as the previously described embodiments of a single, clearly more complex and expensive self-retaining valve.
The locking element provided for conveying the reduction pressure P_Red and/or emergency control pressure P_Not to the clutch control valve in emergency operation is preferably constructed as an emergency valve, which is provided with a concentric pressure chamber, which has a controllable connection of a depressurized line on the spring side, which concentrically has a connection to the control pressure supply line leading to the clutch control valve, and which has a controllable connection of the control pressure line coming from the control pressure supply line or from the self-retaining valve facing away from the spring, as well as with a front-side pressure chamber facing away from the valve spring, which is restricted by an active surface of a piston collar on the spring side and has a connection of a control pressure line conveying a control pressure P_Nor during normal operation.
By means of this emergency valve, it is possible that the valve piston of the emergency valve is displaced to an operating position during normal operation by the application of the control pressure P_Nor, in which the conveyance of the reduction pressure P_Red to the clutch control valve is shut off, and that in emergency operation, i.e. when the control pressure P_Nor is not available, the valve piston is shifted to its idle position by the restoring force of the valve spring, in which the conveyance of the reduction pressure P_Red as emergency control pressure P_Not to the clutch control valve is open. Thus, the emergency operation is activated via the depressurization of the font side pressure chamber of the emergency valve and the consequently induced conveyance of the reduction pressure P_Red, thus converted to emergency pressure P_Not, to the clutch control valve.
For triggering emergency operation, an electrically controllable operation switch actuator, by means of which the control line conveying the control pressure P_Nor to the self-retaining valve and/or to the emergency valve during normal operation can be supplied with the control pressure P_Nor in the powered state of the operation switch actuator and depressurized in the power-off state of the operating switch actuator.
The operation switch actuator can be constructed as a hydraulic solenoid switching valve, e.g. as a 3/2-way switching valve, with a connection of the control pressure supply line, with a connection of a control pressure line of the self-retaining valve conveying the control pressure P_Nor during normal operation and/or of the emergency valve, and with a connection of a depressurized line, by means of which the control pressure line is connected to the depressurized line in the power-off state and to the control pressure supply line in the powered state. The control pressure P_Nor available during normal operation thus corresponds to the reduction pressure P_Red available in the control pressure supply line.
Likewise, the operation switch actuator can be constructed as a hydraulic solenoid control valve, e.g. as a 3/2-way control valve or as a 3/3-way control valve, with a connection of the control pressure supply line, with a connection of a control pressure line of the self-retaining valve conveying the control pressure P_Nor during normal operation and/or of the emergency valve, and with a connection of a depressurized line, by means of which the control pressure line can be connected to the depressurized line in the power-off state and to the control pressure supply line in the powered state. Here the self-retaining valve and the emergency valve can be commutated in series by the solenoid control valve if they have different switching pressures.
Basically, in a dual-clutch transmission with two disconnection type clutches for controlling the clutch control cylinder with a separate execution of the control branches, the constructions and control elements of the control device according to the present invention thus far described can be used in double version. As, however, the expenditure in control elements is inconveniently high in this case, a combined control of both clutch control cylinders that can be implemented by means of a clutch selector valve appears to be more advantageous.
For this purpose, a pressure-actuated clutch selector valve is preferably provided, whose valve piston is spring centered and acted upon in the opposite effective direction by the operating pressures conveyed by both clutch control cylinders via the connection lines, and which has two pressure chambers, each of which has an axial outer controllable connection of the control pressure connection line conveying the emergency control pressure P_Not in case of an emergency operation, an axial inner connection of a depressurized line, and in between a connection respectively leading via a control pressure connection line to the front-side pressure chamber facing away from the valve spring of one of both clutch control valves, whereby the connections of the control pressure connection lines are respectively disposed axially on the side determined by the effective direction of the allocated operating pressures.
The clutch selector valve constructed this way ensures that the reduction pressure P_Red available in case of a disturbance conveyed by the emergency valve as emergency control pressure P_Not, is only conveyed to the clutch control valve of the disconnection type clutch that is still engaged at the moment of the disturbance, as a result of which this disconnection type clutch is engaged or kept engaged, and the other disconnection type clutch is disengaged. This advantageously ensures that both disconnection type clutches can not be simultaneously engaged, as a result of which the vehicle would be locked with gears engaged in both gear trains. Since as at least the self-retaining valve, the emergency valve and the allocated supply and control pressure lines are only necessary in a single version, this embodiment of the control device according to the present invention represents a considerable advantage in terms of costs and installations space.